That time of year is upon us once again when the evenings are about to get a lot lighter but when the clocks go forward many people will be left asking to same question - does it mean we going to lose or gain an hour of sleep?

Computers, laptops and phones usually update the time automatically but for other clocks, it means the chore of going around the house altering them by an hour.

At the end of March the clocks will spring forward an hour at 1am, and in October the clocks fall back an hour at 2am.

And while the downside is that we lose an hour of sleep in March, it does marks the start of British Summer Time.

It means we can start putting those cold, damp, miserable and gloomy days behind us and welcoming in lighter nights so we're not going home from work in the pitch dark.

But what date and time does it happen exactly, and why?

When do the clocks go forward?

The annual custom of putting the clocks forward takes place on the last Sunday of March.

And this year it falls on Sunday, March 25.

They should be turned forward an hour at 1am, so that it becomes 2am.

This is when and why the clocks change in 2018 (Image: BEN STANSALL/AFP/Getty Images)

Don't forget to do it or you will be an hour late for anything you plan to do on Sunday, such as work, sports fixtures, other commitments or appointments, or making it to the supermarkets before it closes early because of Sunday trading laws.

How can I help myself remember to change the clocks?

One key phrase will do the trick: "spring forward, fall back".

When we enter spring on the last weekend in March the clocks go forward, but on the final weekend in October the clocks "fall" back an hour.